Kazuo UEDA, Yoshitaka NAKAJIMA, Wolfgang ELLERMEIER, Florian KATTNER, Intelligibility of locally time-reversed speech: A multilingual comparison, Scientific Reports, 10.1038/s41598-017-01831-z, 7, doi:10.1038/s41598-017-01831-z, 2017.05, [URL], A set of experiments was performed to make a cross-language comparison of intelligibility of locally time-reversed speech, employing a total of 117 native listeners of English, German, Japanese, and Mandarin Chinese. The experiments enabled to examine whether the languages of three types of timing---stress-, syllable-, and mora-timed languages---exhibit different trends in intelligibility, depending on the duration of the segments that were temporally reversed. The results showed a strikingly similar trend across languages, especially when the time axis of segment duration was normalised with respect to the deviation of a talker's speech rate from the average in each language. This similarity is somewhat surprising given the systematic differences in vocalic proportions characterising the languages studied which had been shown in previous research and were largely replicated with the present speech material. These findings suggest that a universal temporal window shorter than 20--40~ms plays a crucial role in perceiving locally time-reversed speech by working as a buffer in which temporal reorganisation can take place with regard to lexical and semantic processing..

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Yoshitaka NAKAJIMA, Kazuo UEDA, Shota FUJIMARU, Hirotoshi MOTOMURA, Yuki OHSAKA, English phonology and an acoustic language universal, Scientific Reports, 10.1038/srep46049, 7, 46049, 1-6, doi: 10.1038/srep46049, 2017.04, [URL], Acoustic analyses of eight different languages/dialects had revealed a language universal: Three spectral factors consistently appeared in analyses of power fluctuations of spoken sentences divided by critical-band filters into narrow frequency bands. Examining linguistic implications of these factors seems important to understand how speech sounds carry linguistic information. Here we show the three general categories of the English phonemes, i.e., vowels, sonorant consonants, and obstruents, to be discriminable in the Cartesian space constructed by these factors: A factor related to frequency components above 3,300 Hz was associated only with obstruents (e.g., /k/ or /z/), and another factor related to frequency components around 1,100 Hz only with vowels (e.g., /a/ or /i/) and sonorant consonants (e.g., /w/, /r/, or /m/). The latter factor highly correlated with the hypothetical concept of sonority or aperture in phonology. These factors turned out to connect the linguistic and acoustic aspects of speech sounds systematically..

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Kazuo UEDA, Yoshitaka NAKAJIMA, An acoustic key to eight languages/dialects: Factor analyses of critical-band-filtered speech, Scientific Reports, doi: 10.1038/srep42468, 7, 42468, 1-4, doi: 10.1038/srep42468, 2017.02, [URL], The peripheral auditory system functions like a frequency analyser, often modelled as a bank of non-overlapping band-pass filters called critical bands; 20 bands are necessary for simulating frequency resolution of the ear within an ordinary frequency range of speech (up to 7,000 Hz). A far smaller number of filters seemed sufficient, however, to re-synthesise intelligible speech sentences with power fluctuations of the speech signals passing through them; nevertheless, the number and frequency ranges of the frequency bands for efficient speech communication are yet unknown. We derived four common frequency bands---covering approximately 50--540, 540--1,700, 1,700--3,300, and above 3,300 Hz---from factor analyses of spectral fluctuations in eight different spoken languages/dialects. The analyses robustly led to three factors common to all languages investigated---the low & mid-high factor related to the two separate frequency ranges of 50--540 and 1,700--3,300 Hz, the mid-low factor the range of 540--1,700 Hz, and the high factor the range above 3,300 Hz---in these different languages/dialects, suggesting a language universal..

Wolfgang Ellermeier, Florian Kattner, Kazuo UEDA, Kana Doumoto, Yoshitaka NAKAJIMA, Memory disruption by irrelevant noise-vocoded speech: Effects of native language and the number of frequency bands, the Journal of the Acoustical Society of America, http://dx.doi.org/10.1121/1.4928954, 138, 3, 1561-1569, 2015.09, [URL], To investigate the mechanisms by which unattended speech impairs short-term memory performance, speech samples were systematically degraded by means of a noise vocoder. For experiment 1, recordings of German and Japanese sentences were passed through a filter bank dividing the spectrum between 50 and 7000 Hz into 20 critical-band channels or combinations of those, yielding 20, 4, 2, or just 1 channel(s) of noise-vocoded speech. Listening tests conducted with native speakers of both languages showed a monotonic decrease in speech intelligibility as the number of frequency channels was reduced. For experiment 2, 40 native German and 40 native Japanese participants were exposed to speech processed in the same manner while trying to memorize visually presented sequences of digits in the correct order. Half of each sample received the German, the other half received the Japanese speech samples. The results show large irrelevant-speech effects increasing in magnitude with the number of frequency channels. The effects are slightly larger when subjects are exposed to their own native language. The results are neither predicted very well by the speech transmission index, nor by psychoacoustical fluctuation strength, most likely, since both metrics fail to disentangle amplitude and frequency modulations in the signals.(C) 2015 Acoustical Society of America..

Emi HASUO, Yoshitaka NAKAJIMA, Erika TOMIMATSU, Simon GRONDIN, Kazuo UEDA, The occurrence of the filled duration illusion: A comparison of the method of adjustment with the method of magnitude estimation, Acta Psychologica, 147, 111-121, (Accepted 4 October 2013; Available online 5 November 2013), 2014.02, A time interval between the onset and the offset of a continuous sound (filled interval) is often perceived to be longer than a time interval between two successive brief sounds (empty interval) of the same physical duration. The present study examined whether and how this phenomenon, sometimes called the filled duration illusion (FDI), occurs for short time intervals (40–520 ms). The investigation was conducted with the method of adjustment (Experiment 1) and the method of magnitude estimation (Experiment 2). When the method of adjustment was used, the FDI did not appear for the majority of the participants, but it appeared clearly for some participants. In the latter case, the amount of the FDI increased as the interval duration lengthened. The FDI was more likely to occur with magnitude estimation than with the method of adjustment. The participants who showed clear FDI with one method did not necessarily show such clear FDI with the other method..

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Yuko Yamashita, Yoshitaka Nakajima, Kazuo Ueda, Yohko Shimada, David Hirsh, Takeharu Seno and Benjamin Alexander Smith, Acoustic analyses of speech sounds and rhythms in Japanese- and English-learning infants , Frontiers in Language Sciences, 10.3389/fpsyg.2013.00057, 4, 57, 2013.02, The purpose of this study was to explore developmental changes, in terms of spectral fluctuations and temporal periodicity with Japanese- and English-learning infants. Three age groups (15, 20, and 24 months) were selected, because infants diversify phonetic inventories with age. Natural speech of the infants was recorded. We utilized a critical-band-filter bank, which simulated the frequency resolution in adults’ auditory periphery. First, the correlations between the power fluctuations of the critical-band outputs represented by factor analysis were observed in order to see how the critical bands should be connected to each other, if a listener is to differentiate sounds in infants’ speech. In the following analysis, we analyzed the temporal fluctuations of factor scores by calculating autocorrelations. The present analysis identified three factors as had been observed in adult speech at 24 months of age in both linguistic environments. These three factors were shifted to a higher frequency range corresponding to the smaller vocal tract size of the infants. The results suggest that the vocal tract structures of the infants had developed to become adult-like configuration by 24 months of age in both language environments. The amount of utterances with periodic nature of shorter time increased with age in both environments. This trend was clearer in the Japanese environment. - See more at: http://www.frontiersin.org/language_sciences/10.3389/fpsyg.2013.00057/abstract#sthash.R2weBtfH.dpuf.